Black Hawk helicopter crash kills 11

A US military helicopter has crashed during a firefight with insurgents in a remote area of southern Afghanistan, killing seven Americans and four Afghans in one of the deadliest air disasters of a war now into its second decade.

The Taliban claimed they gunned down the Black Hawk.

American service personnel are dying at a rate of about one per day so far this year despite a drawdown of troops and dwindling attention on the home front.

That death rate has risen recently with the summer fighting season in full gear and a rash of attacks by Afghan security forces on their foreign trainers and partners.

NATO forces said they could not confirm what caused Thursday's crash and stressed that it was still being investigated.